The present invention relates to coating booth overspray removal systems and, more particularly, to a closed-loop systems which recirculates the working solvent.
In coating operations, it is desirous to reduce overspray to provide an optimum finish on the object being coated. In spray booths or the like, there is generally a ventilation system which draws air downward through a grate into a collection or recovery area. In the collection area, different types of fluid mixtures are used to "kill" or detactify the coating overspray. The "killing" or detactifying of the coating enables the coating to be removed from the collection area without adhering to the sides or removal equipment in the system.
The removal of the overspray coating is of concern in the coatings industry. Particularly, in the automotive industry, where a large number of vehicles are coated with varying types of paints and coating. The removal and disposal of the coating overspray is of great concern.
U.S. Pat. No. 4,750,919 issued June 14, 1988 to Patzelt et. al. illustrates a method for removal of oversprayed paint solids. The method utilizes an oil-in-water emulsion receiving the overspray to "kill" the overspray in the emulsion. Generally, the oil-in-water emulsion includes from 5 to 50 weight percent of an organic liquid having a boiling point of at least 150.degree. C.; from 1.0 to 20 weight percent based on the organic liquid of an oil-in water emulsifier; and the balance water. The oil-in-water emulsion is maintained at a pH value of from 7.5 to 12. The oil-in-water emulsion is continuously circulated in the bath until at least 5 parts by weight of the overspray paint solids for every 100 parts by weight of the organic liquid are received by the oil-in-water emulsion prior to recovery of any material from the emulsion.
While the above system may work satisfactorily, it has disadvantages. In the above system, the paint particles are tied up with the emulsifier which requires continuous removal of the emulsifier layer which, in turn, requires continuous additions of the emulsifier to replenish the emulsion during operation. This is labor intensive and costly to continuously reload the system. Also, continuous monitoring of the pH of the bath must be conducted.
The present invention provides the art with an apparatus and method to reduce the amount of reportable volatile organic compounds. The present invention enables continuous use of the working circulation solvent. The working circulation solvent of the present invention enables portions of the coating overspray to become soluble within the working circulation solvent and other portions of the overspray to be suspended in the working solvent to enable removal of these undesirable elements from the system. Additionally, the system provides for distilling or fractionating of the working solvent to enable removal of undesirable elements and continuous addition of the working circulation solvent back into the system to continuously regenerate the system.
From the following detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.